Anthraquinone pharmaceutical compounds and uses therefor

ABSTRACT

A pharmaceutical compound of the formula ##STR1## in which R is hydrogen, halo or F 2  HCO--; or a salt, amide or ester thereof, useful in the treatment of skeletal diseases.

This invention relates to novel compounds and their use aspharmaceuticals.

The chemical literature describes many compounds derived fromanthraquinone (9,10-dihydro-9,10-dioxoanthracene), for example, BritishPatent 1 578 452, which discloses compounds related to rhein(9,10-dihydro-4,5-dihydroxy-9,10-dioxoanthracene-2-carboxylic acid), aknown compound.

The compounds of the invention have the following formula: ##STR2## inwhich R is hydrogen, halo or F₂ HCO--; or a salt, amide or esterthereof.

Such compounds are useful as pharmaceuticals. They modify cell function,and are indicated for use in the treatment of neuronal, cardiac andskeletal diseases, and also in the treatment of viral diseases, diabetesand associated complications of diabetes. In particular the compoundsare indicated for treating rheumatoid arthritis, and connective tissuematrix diseases such as osteoarthritis and also cancer.

The compounds of the invention have increased stability by comparisonwith similar compounds which tend to metabolise readily by dealkylationto give rhein and related compounds.

In the above formula (I) halo can be fluorine, chlorine, bromine oriodine. Preferred compounds are those of formula (I) above in which R isin the 8-position, and a most preferred compound is of the formula:##STR3## or a salt, amine or ester thereof. Preferred compounds are inthe free acid or salt form.

The compounds of the invention can exist in salt form derived from anyof the well known bases, such salts existing at the 2-carboxyl group.Preferably such salts are pharmaceutically-acceptable, but other saltsare included as they may serve as intermediates in the purification ofcompounds or in the preparation of other salts, or are useful foridentification, characterisation or purification. Examples are thosederived from ammonium hydroxide and alkali and alkaline earth metalhydroxides, carbonates and bicarbonates, as well as salts derived fromaliphatic and aromatic amines, aliphatic diamines and hydroxyalkylamines. Bases especially useful in the preparation of such saltsinclude ammonium hydroxide, potassium carbonate, sodium bicarbonate,lithium hydroxide, calcium hydroxide, methylamine, diethylamine,ethylene diamine, cyclohexylamine and ethanolamine. The potassium,sodium and lithium salt forms are particularly preferred.

An amide is a compound with the substituent --CONR¹ R², and includessubstituents in which R¹ and R² are each hydrogen, alkyl such as C₁₋₄alkyl or an amino acid residue, or together form an alkylene chaincontaining, for example, 4 to 6 carbon atoms. The amide is preferably apharmaceutically-acceptable amide.

The compounds of the invention can also be utilised in ester form, forexample, as an alkyl ester such as an ester of a C₁₋₄ alcohol or abenzyl ester in which the phenyl group is optionally substituted by oneto three substituents selected from, for example, C₁₋₄ alkyl especiallymethyl, C₁₋₄ alkoxy especially methoxy, halo and nitro. The ester ispreferably a pharmaceutically-acceptable ester.

The compound of formula (II) can be prepared by alkylation of the knowncompound, rhein, with chlorodifluoromethane, preferably at a temperatureof from 50° C. to 250° C. and in an aqueous or organic solvent. Othercompounds of formula (I) can be prepared, under similar conditions, byalkylation of an appropriately substituted rhein, such compounds beingdisclosed, for example, in Owton W. M. et al. J. Chem. Soc. PerkinTrans. 1, 1995, 931-934.

As mentioned above, the compounds are indicated for use in the treatmentof osteoarthritis and allied connective tissue diseases such as, forexample, osteoporosis and rheumatoid arthritis. Such diseases are oftencharacterised by an increase in matrix synthesis and remodelling.Incorporation of newly synthesised components into a biological andbiomechanically functional matrix is, however, frequently deficient.Drugs which modulate the activity of the cells involved in suchconnective tissue matrix maintenance and repair are, therefore, ofpotential use in such diseases.

Compounds of the invention produce dose-dependent inhibition of in vitrotumour cell proliferation. Partial inhibitory effects are observed ontumour cell protein synthesis at a concentration of 100 μM using amethod similar to that described by A. Floridi et al, Exp. Mol. Pathol.,1985, 42, 293-305.

Further modulatory effects of the compounds of the invention areobserved in an in vitro model system used to study the differentiationof chondrocytes from prechondrogenic stem cells, as described by D. F.Paulsen et al, In Vitro Cellular and Developmental Biology 24, 138-147.

Further evidence of activity is provided by studying the effect of thecompounds on lesions in guinea pigs. Spontaneous lesions ofosteoarthritis were first described in the hind knee joints of oldguinea pigs by Silverstein and Sokoloff (Arthritis Rheum. 1, 82-86(1958)). Bendele and Hulman (Arthritis Rheum. 31, 561-565 (1988)) andBendele, White and Hulman (Lab. Anim. Sci. 39, 115-121 (1989)) studiedyounger animals and were the first to describe the time course ofprogressing osteoarthritis in outbred male guinea pigs. These latterstudies were confirmed and extended by Meacock, Bodmer and Billingham(J. Exp. Path. 71, 279-293 (1990)), also in outbred male guinea pigs.

The compounds of the invention are thus indicated for use in thetreatment of osteoarthritis and allied connective tissue matrix diseasessuch as, for example, osteoporosis and rheumatoid arthritis.Furthermore, the inhibitory properties on rumour cell proliferationindicate that the compounds are of potential in the treatment of cancer.

The invention also includes a pharmaceutical composition comprising apharmaceutically acceptable diluent or carrier in association with acompound of the invention or a pharmaceutically acceptable salt or esterthereof.

The compounds may be administered by various routes, for example by theoral or rectal route, topically or parenterally, for example byinjection or infusion, being usually employed in the form of apharmaceutical composition. Such compositions are prepared in a mannerwell known in the pharmaceutical art and comprise at least one activecompound. In making the compositions of the present invention, theactive ingredient will usually be mixed with a carrier, or diluted by acarrier, and/or enclosed within a carrier which may, for example, be inthe form of a capsule, sachet, paper or other container. When thecarrier serves as a diluent, it may be a solid, semi-solid, or liquidmaterial which acts as a vehicle, excipient or medium for the activeingredient. Thus, the composition may be in the form of tablets,lozenges, sachets, cachets, elixirs, suspensions, ointments containing,for example, up to 10% by weight of the compound, soft and hard gelatincapsules, suppositories, injection solutions and suspensions and sterilepackaged powders.

Some examples of suitable carriers are lactose, dextrose, sucrose,sorbitol, mannitol, starches, gum acacia, calcium phosphate, alginates,tragacanth, gelatin, syrup, methyl cellulose, methyl- and propyl-hydrobenzoate, talc magnesium stearate and mineral oil. The compositionsof the injection may, as is well known in the art, be formulated so asto provide quick, sustained or delayed release of the active ingredientafter administration to the patient.

When the compositions are formulated in unit dosage form, it ispreferred that each unit dosage form contains from 5 mg to 500 mg. Theterm `unit dosage form` refers to physically discrete units suitable asunit dosages for human subjects and animals, each unit containing apredetermined quantity of active material calculated to produce thedesired therapeutic effect, in association with the requiredpharmaceutical carrier.

The active compounds are effective over a wide dosage range and, forexample, dosages per day will normally fall within the range of from 0.5to 300 mg/kg, more usually in the range of from 5 to 100 mg/kg. However,it will be understood that the amount administered will be determined bythe physician in the light of the relevant circumstances including theconditions to be treated, the choice of compound to be administered andthe chosen route of administration, and therefore the above dosageranges are not intended to limit the scope of the invention in any way.

The invention is illustrated by the following Examples.

EXAMPLE 1

Bis(difluoromethoxy)rhein[9,10-dihydro-4,5-bis(difluoromethoxy)-9,10-dioxoanthracene-2-carboxylicacid]

Rhein (3 g) was dissolved in water/dioxan (1:1) (150 ml). Sodiumhydroxide pellets (5 g) were added and the reaction mixture was stirredand heated in an oil bath to a temperature of 65° C.Chlorodifluoromethane was bubbled into the reaction mixture at a ratesuch that no gas bubbled out. After 3 hours further sodium hydroxidepellets (3 g) were added, reaction continued with chlorodifluoromethaneaddition and the composition of the mixture was monitored by HPLC. After10 hours the reaction mixture was poured into water. A yellow solidprecipitated and was collected by filtration. This solid was dissolvedin hot ethyl acetate. On cooling a yellow solid precipitated and wascollected. This solid was purified by preparative scale HPLC to give thetitle compound which was characterised by ¹ H N.M.R. (δ7.29 (1H, t),7.40 (1H, t), 7.75 (1H, dd), 7.95 (1H, t), 8.03 (1H, d), 8.12 (1H, dd),8.50 (1H, d), 11 (1H, broad).

EXAMPLE 2

Soft gelatin capsule

Each soft gelatin capsule contains:

    ______________________________________                                        Active ingredient                                                                             150 mg                                                        Arachis oil     150 mg                                                        ______________________________________                                    

After mixing together, the blend is filled into soft gelatin capsulesusing the appropriate equipment.

EXAMPLE 3

Hard gelatin capsule

Each active capsule contains:

    ______________________________________                                        Active ingredient                                                                              50 mg                                                        PEG 4000        250 mg                                                        ______________________________________                                    

The PEG 4000 is melted and mixed with the active ingredient. Whilststill molten the mixture is filled into capsule shells and allowed tocool.

EXAMPLE 4

Tablets each containing 10 mg of active ingredient are made up asfollows:

    ______________________________________                                        Active ingredient        10      mg                                           Starch                   160     mg                                           Microcrystalline cellulose                                                                             100     mg                                           Polyvinylpyrrolidone (as 10% solution in water)                                                        13      mg                                           Sodium carboxymethyl starch                                                                            14      mg                                           Magnesium stearate       3       mg                                           Total                    300     mg                                           ______________________________________                                    

The active ingredient, starch and cellulose are mixed thoroughly. Thesolution of polyvinylpyrrolidone is mixed with the resultant powders andpassed through a sieve. The granules so produced are dried and re-passedthrough a sieve. The sodium carboxymethyl starch and magnesium stearateare then added to the granules which, after mixing, are compressed in atablet machine to yield tablets each weighing 300 mg.

We claim:
 1. A compound of the formula ##STR4## in which R is hydrogen,halo or F₂ HCO--; or a salt, amide or ester thereof.
 2. A compoundaccording to claim 1 which is: ##STR5## or a salt, amide or esterthereof.
 3. A compound according to either of claims 1 or 2, in freeacid or salt form.
 4. A pharmaceutical formulation comprising a compoundas defined in claim 1 or a pharmaceutically-acceptable salt, amide orester thereof, together with a pharmaceutically-acceptable diluent orcarrier therefor.
 5. A compound of the formula: ##STR6## wherein R ishydrogen, halo, or F₂ CHO--; or a salt, amide, or ester thereof.
 6. Thecompound of claim 5 in free acid or salt form.
 7. A pharmaceuticalformulation comprising the compound of claim 5, or apharmaceutically-acceptable salt, amide, or ester thereof, incombination with one or more pharmaceutically-acceptable carriers,diluents, or excipients.